Editor's note: Dr. Otis Brawley is chief medical officer for the American Cancer Society and a practicing oncologist. He is CNNhealth.com's Conditions expert and answers viewer questions regularly on CNN.com Live.

(CNN) -- This week, the comedic actress Suzanne Somers is promoting her newly released book, which espouses the virtues of alternative medicine and, more important, explains why one should avoid conventional medicine.

She is a wonderful actress, and I wish she would stick to her first chosen profession. I know some people will hear her message, follow her advice because of her celebrity status and be harmed. Her medical advice may even cause death.

She joins the list of celebrities who have advocated alternative and complementary treatments for disease and non-proven conventional medicine. I have spent much of my professional career documenting disparities in outcome, higher mortality and more suffering among minorities, poor people and even the uninsured middle class who have limited or no access to conventional medicine, the therapies Somers criticizes.

Mind you, I am not critical of the concept of alternative and complementary medicine. When used wisely, it can be useful. Indeed, open-mindedness to other ideas is how we advance conventional medicine. Today, conventional medicine has the extract of a tree bark called aspirin or the root of a plant called vincristine because of observations from those who practiced non-conventional medicine.

My problem is with some and not all of the advocates of alternative and complementary medicine. My problem is with those who reject the scientific method. Some actually do not reject the scientific method. They seem not to even realize that there is such a thing to reject.

Some well-meaning advocates for complementary and alternative therapies are against any rigorous evaluation of these therapies. This allows for quackery. The sophisticated 21st-century snake oil salesmen can make a tremendous profit selling their phony "cures" when there is no adequate assessment by medical peers.

True, there have been some abuses and misdeeds in conventional medicine, and some conventional practitioners offer conventional therapy in unproven ways. I have been very hard on those who abuse conventional medicine. When practiced as it should be, conventional medicine assesses itself and corrects itself when it is wrong.

In the 1980s and early 1990s, many in oncology advocated high-dose chemotherapy and bone marrow transplant for locally advanced breast cancer. Ultimately, rigorous scientific assessment showed this approach to be wrong. Time and time again, we in conventional medicine have, through a process of continuous examination, stopped doing something that did not work or modified a treatment such that it worked better.

Peer review is a central tenet of conventional medicine. In conventional medicine, one must allow experts in ones field to independently review one's data. The fact that a few patients give testimonial to a treatment is not adequate evidence of benefit. Because malignant disease can vary so widely from person to person, randomized controlled phase 3 trials comparing two treatments are often needed to demonstrate that a treatment works. Watch a clip of Somers and Brawley on "Larry King Live" »

Alternative therapies to complement conventional medicine can be useful when done to alleviate a side effect of medicine or discomfort caused by the disease. Such therapies are obviously effective if the patient feels better. These therapies must be discussed with the conventional physician, as they can be devastating when not disclosed to the physician.

Some seemingly innocuous alternative treatments can be harmful. The anti-HIV drug DDI is inactivated when taken with high doses of vitamin C. Some HIV patients who secretly took high-dose vitamin C as a complementary therapy with DDI harmed themselves.

While conventional medicine is by no means perfect, and those who practice it are often flawed, the wise use of proven conventional therapy is responsible for a tremendous decrease in the mortality rate (risk of death) over the past century.

I encourage all patients who choose to use alternative and complementary medicine to discuss it with their conventional physician. Remember, some therapies that are label-alternative and complementary can be reasonable and helpful. Some can be harmful.